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Akka/Scala example source code file (PersistentViewExample.java)

This example Akka source code file (PersistentViewExample.java) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorref, actorsystem, akka, concurrent, duration, exception, override, persistence, persistentviewexample, procedure, snapshotoffer, string, time, untypedpersistentactor, untypedpersistentview

The PersistentViewExample.java Akka example source code

package sample.persistence;

import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.japi.Procedure;
import akka.persistence.SnapshotOffer;
import akka.persistence.UntypedPersistentActor;
import akka.persistence.UntypedPersistentView;
import scala.concurrent.duration.Duration;

import java.util.concurrent.TimeUnit;

public class PersistentViewExample {
    public static class ExamplePersistentActor extends UntypedPersistentActor {
        @Override
        public String persistenceId() { return "sample-id-4"; }

        private int count = 1;

        @Override
        public void onReceiveRecover(Object message) {
          if (message instanceof String) {
            count += 1;
          } else {
            unhandled(message);
          }
        }

        @Override
        public void onReceiveCommand(Object message) {
          if (message instanceof String) {
            String s = (String) message;
            System.out.println(String.format("persistentActor received %s (nr = %d)", s, count));
            persist(s + count, new Procedure<String>() {
              public void apply(String evt) {
                count += 1;
              }
            });
          } else {
            unhandled(message);
          }
        }
    }

    public static class ExampleView extends UntypedPersistentView {

        private int numReplicated = 0;

        @Override public String persistenceId() { return "sample-id-4"; }
        @Override public String viewId() { return "sample-view-id-4"; }

        @Override
        public void onReceive(Object message) throws Exception {
            if (isPersistent()) {
                numReplicated += 1;
                System.out.println(String.format("view received %s (num replicated = %d)", message, numReplicated));
            } else if (message instanceof SnapshotOffer) {
                SnapshotOffer so = (SnapshotOffer)message;
                numReplicated = (Integer)so.snapshot();
                System.out.println(String.format("view received snapshot offer %s (metadata = %s)", numReplicated, so.metadata()));
            } else if (message.equals("snap")) {
                saveSnapshot(numReplicated);
            } else {
              unhandled(message);
            }
        }
    }

    public static void main(String... args) throws Exception {
        final ActorSystem system = ActorSystem.create("example");
        final ActorRef persistentActor = system.actorOf(Props.create(ExamplePersistentActor.class));
        final ActorRef view = system.actorOf(Props.create(ExampleView.class));

        system.scheduler().schedule(Duration.Zero(), Duration.create(2, TimeUnit.SECONDS), persistentActor, "scheduled", system.dispatcher(), null);
        system.scheduler().schedule(Duration.Zero(), Duration.create(5, TimeUnit.SECONDS), view, "snap", system.dispatcher(), null);
    }
}

Other Akka source code examples

Here is a short list of links related to this Akka PersistentViewExample.java source code file:

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